Question PSU buzzing randomly for a short time

[CiprianGraphics]

Ok so I have a bit of a problem which I might need some help with.

I have a Corsair RM850x 850W modular power supply that I bought for my computer and I have a situation with it. I will try to explain it in detail so it might be a long post, but it is simply something that eludes me completely.

Basically, my PSU used to make random buzzing sounds, rarely. Sometimes once per day but mostly once every few days, I would hear a very short duration ”electrical-like” buzzing sound, for no apparent reason. This buzz typically lasted less than a second, and was not necessarily very audible, but audible enough so that I would hear it in a silent environment (my computer is generally very silent, even on a medium load). From what I have searched on forums and such, this would be described as coil whine. However, this PSU has a very slight, barely audible coil whine which is continuous but cannot be heard unless I actually move my ear very close to the PSU, and i would describe it as a high-pitched humm-like sound. But the electrical buzzing sound that I described earlier hearing randomly is different from that and can be heard even when i am a couple of meters away from my unit.

At some point I noticed this electrical buzzing sound being heard in the evening, so I assumed that it is probably due to the fact that in the evening, power consumption in my 5 story building may increase due to people returning home from work and turning on their various things inside their homes, and might mess the building's electrical grid, and since I am no electrician, I have no idea if this assumption is correct or not. So what I found out is people having similar problems due to a messed up electrical grid inside their homes. The RM850x is overkill, since i rarely if ever went above 350-400W in power consumption with my current computer components, so it is not a question of overloading it. And from what I know, if a power supply cannot power up the computer completely, it shuts down.

So since i have a very very slight, barely audible coil whine in it that I am aware of (and is normal), and if i don't listen closely to the PSU i cannot even hear it, I assumed this random electrical short duration buzz wasn't something natural. So I bought a 1200W line-interactive UPS, with pure sine wave output. The UPS works normally ever since i bought it, and it shows in the evening a voltage of around 234-235V, being in a 230V socket, which is normal (I live in Eastern Europe and the accepted tolerance for this kind of thing is a +/- 5% from the total voltage). I connected my computer and my computer screen to it, and nothing else. In idle i have around 50-60W consumption in total from my UPS, so the question of my 1200W UPS being not enough is totally out of the question. Closing on full load, i rarely went over 350W if ever in total power consumption from the UPS.

Since I had the UPS, I rarely if ever heard that buzzing sound again, until one day. That day I came home and when I turned the lights on in my room, the wall socket, the UPS and the PSU all started emitting an audible electrical buzzing sound which didn't last very much, because I got scared and pulled everything out from the wall socket. The computer was NOT on. I plugged it again in a different wall socket in another room after 10-20 minutes. The new socket did not emit any kind of strange sound, neither did the UPS. I still had, however, an electrical buzzing sound coming from the PSU which lasted for about 10 more minutes and eventually faded out by itself. So i concluded that something was definitely wrong with the wiring, at least in that section of the house. I removed the lights in the room completely and continued to use the new socket until I called an electrician who changed the wall socket in my room, tested everything (and it seemed to be working properly) except the wiring in my lights who were not properly isolated (i think it is called like that, sorry for my English) and we concluded that it might have been some electrical arc in the lights wiring that triggered the whole buzzing sound experience. That got tested and fixed, and ever since, the computer and the UPS didn't behave like that anymore (it has been a few weeks now).

However, nowadays, every now and then, i still hear a short buzzing sound every now and then, it only did so 2-3 times so far, and every time this buzz lasts less than a second. I have to mention the fact that during these buzzes, absolutely nothing changes in the computer performance, nothing freezes, everything works perfectly, the voltage shown by the UPS is normal, the voltages showed by my mainboard in BIOS are also within normal parameters, in other words, everything is normal, except for the short buzzing sound. I have no idea what is causing it, since i cannot identify a real pattern as to how and when they occur.

After telling all this long story, I have a couple of questions:

1. Is this short buzz (that lasts less than a second and occurs rarely) something normal or something that I should be worried about? Mentioning again the fact that the computer doesn't seem to be affected performance-wise in that moment at all. I also want to mention the fact that all my computer parts have been tested individually and seem to be working properly. In other words, should I worry?
2. Can this short buzz happen due to the fact that my PSU is modular and perhaps the wire connections to the PSU (which I believe i fitted properly, I checked and double-checked a lot of times) behave like that in a normal way?
3. Is this kind of sound normal with power supplies in a silent environment? (Before I bought this new computer, everything I owned in the past was fairly noisy due to having slightly noisy fans that would cover the sound if it had happen before, so therefore I wouldn't know)
4. Is this kind of sound normal with the Corsair RMx series? I heard people being unlucky and getting noisy PSUs. If it is just the noise, I would ignore it completely.
5. Is this kind of sound indicating a more serious problem that would occur in the future?
6. Could the electrical grid still be to blame, since the changing of the electrical wiring in the lights and the wall socket may not have fixed the problem completely?

I have to mention a few other things as well:

• before I got this Corsair RMx I had a Cooler Master G750M 750W power supply which buzzed the same way, randomly every now and then, but sometimes the buzzes would last even a couple of seconds or even minutes. But now I understand the improper wiring in the lights in my room would have distorted the grid, so that was one of the main causes, as I am still not sure if it was the only one.
• my current computer configuration is this:

- Cooler Master MasterCase MC500 with tempered glass cover, because I needed space to move inside it;
- the aforementioned Corsair RM850x PSU;
- Intel i9-9900k cooled nicely by a Noctua NH-D15 air cooler with 2 spinning fans, cooled even on Turbo Mode;
- ASUS TUF Z390 Gaming Plus 1151v2 socket motherboard;
- Two kingston SSDs, one of 480 GB and the other one of 240GB capacity;
- a Palit nVidia RTX 2070 video card;
- two 16GB Kingston HyperX Fury sticks of DDR4 memory;
- a pair of headphones attached to the frontal panel of the case, but nothing else external;
- an ASUS 19inch computer screen which I believe has no relevance in the buzzing of the PSU;
- an nJoy Argus line-interactive UPS with the output capacity of 1200W and two new, tested and fully working batteries;

• i have a Wireless gigabit router on my table at a distance of around 20-30 cm away from the PSU;
• the computer case, the screen and the router all stand on my desk;
• the PSU fan is not spinning on idle and it is dead silent spinning on medium to full load, so I ruled this out as a possible cause for the buzzing sound because:
• the buzzing sound, to the best of my knowledge, happened on idle or mostly idle, not on full load;
• the wiring in my house, to the best of my knowledge (i didn't make it nor was I there when it was made) is properly grounded;
• I rarely experience blackouts, if ever, but I bought the UPS to try to fix any "impurities" in the current flowing to my PSU, and brown-outs are not a thing in my area (the last brown-out that I remember happened some years ago, and before that I can't remember any);
• I read about common noises in PSUs and not everything can be described as coil whine, even if some things can sound similarily. There are other pieces in there that can emit sounds.
• after the wall socket was replaced and the wiring of the lights was fixed and tested, I only heard this buzzing sound 2 or 3 times (the fixing happened around 3 weeks ago).

Any relevant information would be much appreciated, and it would put my mind to rest to know that this is actually a harmless noise and can happen due to some normal magnetic field related phenomenon, but I don't want to speculate since I am not an electrician and still have a lot to learn about these things.

Edit 1: I think I posted this in the wrong forum section.

 

[Mezoxin]

would you record that buzzing sound that is audible from several meters

 

[CiprianGraphics]

would you record that buzzing sound that is audible from several meters

I would if i could, but since it happens randomly, rarely, and it lasts less than a second, I must be very lucky to be able to do so. But let's see if i find an example video on Youtube or something.

 

[CiprianGraphics]

would you record that buzzing sound that is audible from several meters

This is the exact sound here: https://www.youtube.com/watch?v=zdpl683oLRM
The difference is that mine lasts a very short amount of time and can't predict when it happens, since i am not able to reproduce the conditions leading to it.

 

[Mezoxin]

do you hear that sound when the pc is off as well ?

 

[CiprianGraphics]

do you hear that sound when the pc is off as well ?

I never hear it when the PC is off. The only time that I heard it when off was during that event when I turned the lights on in my room and the wall socket, the UPS and the PSU started to buzz at the same time. That happened when the PC was off, as I turned the lights on with the idea of also turning the PC on after that. And after I plugged everything back in the new wall socket, the PSU continued to emit that sound for a few more minutes, after which it faded and stopped on its own.

 

[grimfox]

You are absolutely positive that the sound is coming from the PSU and not the UPS? The UPS will (most models) perform a self test every so often. During this test it will disconnect the mains power and run a test which will cause a buzzing sound. On mine it does anyway. Mine usually does this in the morning on Sundays which is when I scheduled it. If you haven't scheduled it then it may do it sporadically. Or if your schedule changes frequently it may have always been doing this but you haven't noticed the pattern as you aren't around when it triggers.

If it is actually the PSU and it's bothering you, pick up a new one. Piece of mind is sometimes worth the expense versus not knowing. Generally there is no situation where the PSU should be making a buzzing noise. It's possible that a surge in your building has slightly damaged the PSU prior to being protected by the UPS. With the UPS in place there is no reason for a new PSU to be in question.

 

[CiprianGraphics]

You are absolutely positive that the sound is coming from the PSU and not the UPS? The UPS will (most models) perform a self test every so often. During this test it will disconnect the mains power and run a test which will cause a buzzing sound. On mine it does anyway. Mine usually does this in the morning on Sundays which is when I scheduled it. If you haven't scheduled it then it may do it sporadically. Or if your schedule changes frequently it may have always been doing this but you haven't noticed the pattern as you aren't around when it triggers.

If it is actually the PSU and it's bothering you, pick up a new one. Piece of mind is sometimes worth the expense versus not knowing. Generally there is no situation where the PSU should be making a buzzing noise. It's possible that a surge in your building has slightly damaged the PSU prior to being protected by the UPS. With the UPS in place there is no reason for a new PSU to be in question.

Thank you for your input. Yes, it has nothing to do with the UPS. The UPS is generally dead silent. I did not schedule a self-test but i test it myself every now and then. There is a small piece of software called PowerMaster, which allows me to manage and test the UPS. When such a test occurs, the UPS starts humming, initially a bit loud, noticeably loud, and then the sound slowly fades away during a 2 hour time period, after which it stops completely. This humming is a very specific sound that can be heard even from 20 meters away. Other than that, dead silent in any circumstance. Apart from that, PowerMaster has an event log that would record any anomaly with the UPS if it happens. According to the log, everything works smoothly.

However the sound that i am describing comes from directly inside the PSU. Having a short duration of less than a second does not allow me to find out from exactly which part of the PSU it comes. And is an identical buzzing sound like the one recorded in the Youtube video that I posted earlier in the reply to Mezoxin's comment, except for the short duration. The guy in the Youtube video has a PSU that buzzes constantly. It is not a loud sound, but in a silent environment, i can hear it from about 3-4 meters away. It is possible that the PSU may have been damaged the moment I turned the lights on in my room but then I ask myself how is it still working now, without giving any sign of being or turning defective. I have not seen many PSUs die, but the ones that did, either went out with a bit of a bang or they died slow deaths with symptoms like turning the computer off at random times, computer freezes and other stuff.

What is killing me is not the sound itself. If it was constant, i would have probably labeled it "coil whine" and would have been able to live with it without problems. What kills me is not knowing what is making it. I assume I "cleaned" the electrical current flowing through my UPS towards my PSU and since all the other parts inside the computer have been independently tested and gave good results, then I really have no idea why this happens.

The other PSU, the Cooler Master that I mentioned in the initial post, buzzed a lot more, and one or two times it even lasted minutes, but it still works even now. That PSU was the reason I bought this Corsair in the first place, thinking it was a faulty PSU, because even if i would have sent it back to the store, I still needed an extra PSU to run my computer because i also do my job on it (i work from home). Turning the lights on in the room allowed me to pinpoint the fact that it was not the PSU but the electrical grid in this part of my home. Also, I wouldn't call this a surge, but it was rather something similar to a brown-out or the kind of event that happens when you flip a light switch partially on, and the light flickers because there is not a full contact made within the internal circuitry of the switch.

I also checked everything inside the case to be well fitted in, because i built this rig myself.

I only have three theories:
1. I have heard that the voltage regulator inside a PSU can emit noises when the electric current flowing towards the PSU is "dirty". That would explain the same sound being heard also in the UPS during that light switch event. I don't even try to explain the sound in the wall socket since the wall socket itself was rather old and needed changing anyway. When I did change it, however, it showed no traces of being burnt or anything. Old but clean, but I did not trust it anymore even so. I have no idea how a voltage regulator behaves under such conditions or sincerely any other abnormal conditions, so it could have emitted the sound. If that is the case, I would suspect it to be a bit more sensitive towards certain fluctuations and would emit a short buzz if something not right were to happen but not "too not right" to cause any actual damage. But it is also possible that I have no idea what I am talking about, and I merely speculate.

2. This can actually be coil whine and maybe i have special coils that would emit sounds every now and then, rarely and randomly, since there is a barely audible coil whine to begin with when I put my ear very close to the PSU. Maybe that increases for half a second sometimes just to scare the hell out of me and troll me, i have absolutely no idea.

3. Being a modular power supply, the connections between the cables and the PSU may not be perfect, and every once in a while there is an electrical sound inside those areas because of this, kind of like the sound that some electronics might make when you plug them into a socket, but this is again speculation.

Except for this weird sound, everything works as it should.